RE: [TCML] Double-layer secondary coil

["Lau, Gary" <Gary.Lau@xxxxxx>]

One should take reports of a 10% spark improvement with a grain of salt.  In my experience, measuring sparks is highly subjective.  Even if nothing is changed, if I measured the best spark length on a coil, turned it off, then tried to repeat the measurement, a 10% or more deviation is not surprising.  This is one of the things that makes our task so challenging!

Adding a second layer on top of a secondary winding should not significantly alter its inductance - it would only reduce the DC resistance by about half.  The inductance would only be reduced if the two layers were not coupled to each other.  While a 50% resistance reduction may sound like a significant benefit, it's important to also consider the relative magnitude of the load (streamer) impedance.  Don't quote me on this, but I think the equivalent modeled streamer impedance turns out to be something like 150KOhms in series with a few pF per foot of streamer length, to ground.  So if your secondary coil has a resistance of 500 Ohms and you have the opportunity to reduce that to 250 Ohms, the fact that it's driving a MUCH higher load impedance means that the reduction in losses will be negligible.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of otmaskin5@xxxxxxx
> Sent: Sunday, February 03, 2008 2:30 PM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Double-layer secondary coil
>
> I thought Gary Weaver's post of 3 or 4 weeks ago was interesting.? He reported
> getting ~10% increased spark length after winding another layer of wire over the
> first layer of his secondary.?
>
> I'm trying to understand the principle behind the increased performance.? It seems
> clear that the additional layer reduces the secondary coil's resistance?by about half
> which would support longer sparks.? But it seems like the double-layered coil would
> also reduce inductance which would reduce spark length.
>
> I'm not sure what the the additional layer's?impact is on the secondary's
> inductance.? I believe 2 identical coils wired in parallel would reduce total
> inductance by 1/2, but does the double layer configuration also have an effect I'm
> not taking into consideration???If so, is there a formula to calculate secondary
> inductance in this configuration??
>
> Or does the reduction in resistance somehow out-weigh the reduction in inductance
> in terms of spark length??
>
> I'd appreciate any thoughts on this.? Thanks, Dennis Hopkinton MA
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